Touch pads in general are described in e.g. U.S. Pat. Nos. 4,346,376, 4,484,179, 4,688,933, 4,710,760, 5,484,966, 5,945,981, and 6,122,394, JP07036603, JP03216719, as well as US 2003/0048257 and 2003/0052257.